1. Field of the Invention
The present invention relates to a structure for fixing an element (e.g., an auxiliary printed wiring board unit for updating of software or hardware) to a printed wiring board, and also to electronic equipment (e.g., a portable information processing device) having the fixing structure.
2. Description of the Related Art
In electronic equipment such as a portable information processing device, an auxiliary printed wiring board unit is independently provided on a printed wiring board in some case, so as to increase a mounting area per unit volume. In general, electronic components including IC chips are mounted on both surfaces of each of the printed wiring board and the auxiliary printed wiring board unit. Accordingly, in the case of providing the auxiliary printed wiring board unit on the printed wiring board, a spacer is interposed between the printed wiring board and the auxiliary printed wiring board unit to fix the auxiliary printed wiring board unit onto the printed wiring board. That is, the spacer has a first end fixed to the auxiliary printed wiring board unit and a second end fixed to the printed wiring board, thereby fixing the auxiliary printed wiring board unit to the printed wiring board with a predetermined space defined therebetween.
To fix the second end of the spacer to the printed wiring board, the printed wiring board is formed with a hole so designed as to be fitted with the shape of the spacer, for example. The second end of the spacer has a projection adapted to be inserted into the hole of the printed wiring board. By filling the hole with a sealant such as a solder in the condition that the projection is inserted in the hole, the second end of the spacer is fixed to the printed wiring board. The auxiliary printed wiring board unit is fixed to the first end of the spacer by means of a screw, for example, in consideration of replacement of the auxiliary printed wiring board unit.
The length of the projection formed at the second end of the spacer is set sufficiently larger than the thickness of the printed wiring board. As a result, when the spacer is fixed to the printed wiring board, the projection of the second end of the spacer inserted in the hole of the printed wiring board largely projects from a first surface of the printed wiring board opposite to its second surface for fixing the spacer, causing a difficulty of reducing the size (especially, thickness) of electronic equipment.
Further, since the projection of the second end of the spacer projects from the printed wiring board, an electronic component cannot be mounted on a portion of the printed wiring board around the hole, causing a limitation to an increase in mounting area of the printed wiring board.